In order to accomplish an increase in the strength and/or mass of a muscle, the muscle is generally overloaded. One of the most common ways to achieve muscle overload is through repetitive lifting of weights, sometimes referred to as resistance training.
In the martial arts there is a series of blocking maneuvers that rely on external rotation of the forearm. The blocks are sometimes converted into grabs of an opponent's arm or directly into strikes at the opponent. Finger strength is important for certain advanced techniques that entail striking the opponent with tips of the fingers and then grasping their flesh to induce pain. In Okinawa, Japan, the geographic origin of karate, exercises to develop arm strength for these maneuvers were traditionally done with stone weights at the end of short wooden shaft. As karate students became stronger they got bigger stones to work with. Karate students developed finger and hand strength by grasping with their finger tips the lips of clay jars filled with sand. The jars would then be picked up and carried about. The amount of sand was increased as the students became stronger. In the United States the traditional methods are sometimes used today with cement blocks at the end of a shaft and various traditional and contemporary exercises are utilized for developing finger strength.